Samsung
Turn Lock Instantly with Side Key On or Off auf Samsung
Lock instantly with Side key is a separate setting from Lock automatically, even though both control when your screen locks. The side key option forces an immediate lock every time you press the power button, no matter what delay is set elsewhere.
Lock automatically works on a timer that starts after the screen turns off by itself. If that timer is set to a short delay, you can still unlock the phone briefly after pressing the side key before the pattern, PIN or password screen appears. Turning off Lock instantly with Side key removes the forced lock on button press and leaves only the automatic timer in control.
Where to find the setting
Go to Tap on Settings ➔ Tap on Lock screen ➔ Tap on Secure lock settings ➔ Enter the current Pattern,PIN or Password ➔ Enable or disable Lock instantly with Side key.
You only see this option once a secure lock screen method is active. Disabling it does not remove your lock screen, it only changes how quickly the lock engages after you press the side key.
If you want the screen to stay unlocked briefly after pressing the button, turning this off is the right fix. If you want maximum security regardless of timers, keep it enabled.